Telephone system



April 23, 1929. E. DIETZE TELEPHONE SYSTEM Filed July 192 INVENTOR.

'A TTORNEY Patented Apr; 23,1929.

un ts srarss nenvnnnn nrnrzn', or wEsTrInL-n, new mess Assienon To AMERICAN Tenn 7 Pnonn Ann TELEGRAPH COMPANY, A conrona'rion or new 'YGRK.

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Application filed Jui e, 1927. Serial No. 293331."

This invention relates to telephone circuits,

and particularly to telephone sets which may fbefe nployed for the interconnection of two or more circuits so that telephonic communication maybe established thereover. I i

- Several new operating schemes in use at the present time permit a telephone subscriber to j v y Call 011C111t maybe connected to the trunk cir- 1 cuit through'the operators telephone'set, Fig.

ring his operator and remain on the telephone circuit while the operator establishes the proper connection. By these practices, a subscriber isenabled to catch mistakes made by his operator in communicating the telephone number to another operator connected to another circuit. 'Thus, the subscriber may frequently prevent his operator from connecting his circuit to an undesired circuit. Obviously, this results in faster and more eflicient telephone service.

In accordance with these practices, the operator7s set is frequently connected to two circuits simultaneously, (1) the trunk circuit extending to the city orexchange which is being called at the endo'f which there is a B operator and (2) the subscribers circuit r which connects the subscriber with the A operator. If the ordinary operators telephone set be connected to two such circuits simultaneously, the transmission efficiency, so far as the operators set is concerned, is considerably reduced because of the fact that one of the circuits introduces a bridged-loss for the other. Yet, the subscriber may hear the conversation on the trunk circuit between the A and B operators, because the subscribers circuit and the trunk circuit are interconnected through the operators telephone set.

- To permit the subscriber to hear a conversa- 'tion between operators overfa trunk circuit may,*nevertheless, be objectionable for vari ous reasons.

In accordance with this invention, an operators telephone circuitwill be described which, when connected to two or more telephone circuits,'will prevent the transmission loss" heretofore introduced by-bridging one .circuitacross another circuit. Moreover, the proposed operators telephone circuit will substantially prevent the transmission of telephonic signals between the subscriber and a party or operator connected 'to the distant endof the trunk circuit during the period in which circuit connections are being established.

This invention from the detailed description hereinafter tolwill be better understood telephone circuit.

lowing,when read inconnection with the accompany ng drawing in wh ch Figure 1 rep-;

resents thecircuit arrangement of a call circuit and a loop circuit connected through an. operators telephoneset, Fig. 2 shows a similar circuit embodying the principles'of this invention inwhich a balancing network or a 3 shows the general arrangement of the ele- 'principlesof the invention, and Fig, tshows two telephone circuits either or both of which may be connected to an operators telephone Referr ng to Fig. 1 of thedrawing, a tele phone line L is shown which may be, bridged by a call circuit C. The telephone circuit L terminates inanoperators telephone set comprising three Windings wound on a common I core; The first windingais in series relationship with a telephone transmitterT of I well known type of, for example, the carbon button type,while, the second and thirdwindings a and dare in series'relationship with the telephone circuit L. A telephone receiver R of any we'll'known type bridges the telephone} circuit L from the-point common to the latter windings. A balancing network N which,

although shown in the form'ofa resistance, may in general cons1st.ofreactance as well as i'esistance of suitable magnitudes, is in series relationship with windingd."

The circuit arrangement shown in Fig. l illustrates a system in wh ch-speech repetition on thecall circuitor circuits may be restrict- The operator controlling the telephone set having the transmitter T and the receiver R is known as the'A operator, while the party or operator at the distant end of the telephone line L is known as the B operator. The subscriber at the distant end of the call circuit C may be connected to thetelephone line L by a. the A operator. When such. a connection is established, thesul'iscribe'r hears the A operavtor pass'his call over the telephone circuitL,

thesubscriber usually remaining connected to "the telephone circuit L1 1 The telephone circuit L is thus bridged by the call circuitC, introducing a substantial loss in eiti ciency so far as the Aoperators telephone set is concerned. Accordingly, the subscribed may converse with the B operator and he-m'ay. also hear the voices ofditferent operators connected to the A modified circuit arrangement based on the pr nciples of this invention 18 shown in Fig. 2. Here a condenser K is shown in series with the telephone receiver R, bridged acrossthe telephone circuit L from the point common to windings and cl. When a call circuit key (not shown) is depressed, the

armatures, e and 7, which are energized by an electromagnetic Winding (not shown). move outwardlyso as to connect the call circuit C to the operators telephone set instead of the balancing network N. key is released, armatures e and f move inwardly so as to disconnect the call circuit C and then terminate the operators telephone set with the balancing network N.

It is to be "observed that in thisinvention,

the balancing network is disconnected from an antiside tone telephone circuit of a well known type when the operatorstelephone set is being connected to a second circuit or line such as the call circuit C. Thus the seco'nd'circuit or line, i; e., call circuit C, is substitute d'in plac'eo'f the balancing network N. Call circuit C then actslas a balancing neti work for the first line, i. e, the telephone circuit L. It is obvious-that theselines must have a proper impedance relationship for good side "tone balance. This relationship will exist in an operators telephone circuit arrangement which is terminated in the balancing network N if "Tam which L-is the impedanceiofthe telephone connected in series relationship therewith, Then fee.

lineL,'N is the impedance of the balancing network and c and Z represent the number of turns on the respective windings. Vhen the call circuit key is'depressed so as to connect the call circuit C to the operators telephone set in place ofthe balancing iietworl tlien'N will representthe impedance of the-latter circuit. v p

It can readilybe understood that in the telephone substation of the type under consideration, no energy-is dissipated in. the

balancing network when signals are being received, and furthermore, no energy can be transmitted from the balancing network to circuit L if, for exan'iple, a transmitter were in which T and R arethe impedances of the transmitter and receiver,- respectively, a is the number of turnson the winding in series with the transmitter Tiandc and (Z are the 'number of turns on the wi 'idings coupled to winding a If the l circuit ai'rangeinent shown, in which the telephone line L is con nected to the call circuit C, were designed to provide the relationship expressed in Equa- YVhen the call circuit windings b and 0.

tion then the transmission of signals beti "sen the telephone line L and the call circuit C will. be practically eliminated. Itbecomes appar-ent'froin Equation (2), however, that the relative magnitudes of the transmitter and receiver impedances must be carefully proportioned and that these elements must also bear a proper phase relationship. Thus, the condenser K is shown in series with the telephonereceiver R andthis condenser may be used for adjustment so as to bring about theproper phase relationship. Yet,

such a condenser will bring about suitable phase equality only over a comparatively narrow band of frequenc es. If it isjnecessary to provide phase equality over a wider band of frequencies, theninductance maybe added in series with the transmitter T inv stead of a capacity, such the condenser K in series with the telephonereceiver R, It is here to be noted that the condenser'in series with the telephone receiver has a practical ad "EilliZLQQ over the inductance in series with the lraiisu'iitter, tlie series inductance introducing a substantial transmission-loss while the series condenser provides a transmission gaiii. 'lhus, the series condenser is deemed preferable to the series inductance in practical circuits. if satisfactory suppression of signaling currentsbetween tl'ielfi operator and the subscriber is to be obta-inedby the phase adjustment which may, for example,

bemade over a comparatively narrow'frequency rangeby changingtlie capacity of said v condenser.

' Referring'again to Fig. 2 of the drawing,

it will be seen that when the call circuit key isdepressed to replace the balancing network by the call circu t C, the telephone line L then'acts as a balancing network and does not, of itself, introduce any transmission loss.

If, however, the telephone receiver and transinitter are suitably proport oned, a large transmission loss will be introduced between the telephone line L and the call circuit C'so that the trans i'iission of speech signals over these circuits while the operatcfs telephone set 'is co'iinected will be substantially pre-v vented. I V

Fig. 3 shows a circuit arrangement in which two lines L and L are shown interconnected by an operators telephone v i indings b and care in series relat onshipwith lines L,

and L and a telephone receiver R bridges i lines L andL from a point common to liar ease of local straightforward lVind'ing a is coupled .to windings 0 and c and is in seriesiwiththe o well as the listening key M. When the splitcar rangement shown in'Fig. 3 in which a listening key Mand a splitting key S are employed. hen the listening key is in its normal position,' line'L is directly connected to'line L through armature 10 and contact 11, and armature 12 andcont-act 13. By depressing between circuits L and L The upper branch of these circuits may be traced through armature 10, contact 1 1, contact '18, armature 19, windings g and h, armature 20, contact 21, contact 16 and contact 11. The

lower branch of these circuits may be traced from armature 12 through contact-15, contact 20, armature 21, windings Z and m, armature 22, contact 23'and contacts 17 and 13.

The depression of listening key IVT'PIOVlClGS a circuit similar to the one shownein Fig. 3, in which the windings in series with thetelephone lines L and L are divlded between J the two sides of the interconnected circuit primarily for the purpose of symmetry. Thus, the operator may converse with a party connected to either of the lines. When the operator converses over line L the conversation may be heard over line L If any misstatement isma-de by the operator,'she

"may be interrupted and notified of her misstatement in order that it may be corrected. Obviously, this is equally true of conversations by the operator over line L The operator may talk over eitherline independently by operating the splitting key S as ting key S is thrown to the right, the listening key M being closed, the armatures 20 and 22 v will close contacts 2 1- and 26, respectively.

The operators telephone set is then connected to line L the operators set'bcing terminated in impedance N The latter-circuit may be traced through armature 10, contact 14, contact '18, armature 19, windings g and 71,, ar-- mature 20, contact24, impedance N contact 26, armature 22, windings m and Z, armature 21, contact 20, contact 15, and armature 12. Thus. it will be apparent that when the listen ing key is closed and the split-ting key is thrown to the right, the impedance N replaces the line L and the operator may ,con

verse with the party at the other end of the line L,. Similarly, by closing the listening key M and by throwing the splitting key S to the left, line L, may be disconnected and line L connected to the operators telephone set.

The latter circuit may be traced through contacts 11 and 16,'contact 21, armature 20,wind

ingslhand'g, armature 19,'contact 27 iinped-,

an'ce N ,'co11tact28, armature 21, windings Z and m, armature'22, contact 23 and contacts 17- and 13. 'Thus, it will'be apparentthat when the listening key is closed and the splittitng key is thrown to the'left, the operator may converse with the party at the other end ofline L the balancing network N replacing-the line L,. If networks N and N have impedan ces substantially equal to the impedances-ot L and L respectively, good side {tone-balance will be obtained.

' I lVhile this invention has been pointed out in certain partitcular arrangements merely tor the'purpose of illustratiomit is to be distinctly understood that the principles of this inve'ntion may be applied to other and widely varied organizations without departing from the spirit of the 1I1YIlt1011-OlthQSCOpe of the 1. A telephone system comprising a trunk i circuit, a subscribers line, an operators telephone set including a telephone transmitter and a telephone:r'ecelyer,.means interconnecting the trunk circuit and the subscribers line through the op'erators telephone set wherebythesubscriber'may hear the conversation of the operator over the, trunk circuit though unable to communicate with any one at the distant end of the trunk circuit.

2. In a telephone system, the combination of two loops which may be interconnected for telephonic communication,- means for inter-posing between said loops a telephone set comprlsmg a telephone transmitter and a telephonelreceiver, whereby communication may be established over either of said loops from the telephone set-'while a large transmisslon loss Wlll be mtroduced between said-loops preventing telephonic co1'mnunicationover said loops.

3. A telephone system comprising two lines overwhichsignals may be transmitted, a

telephone circuit arrangement comprising an inductance in series with said lines, a tele-; 7 phone rece ver connected to the mid-point of said inductance and to a terminal common to said lines, and atelephone transmitter coupled to said inductance, two in'ipedances,

each simulating the impedanceof one of said lines, and means whereby the telephone cir cult arrangement may. be connected to one f lating the other ofsaid lines. 1

4. A telephone system comprisingtwo telephone loops, a' transformer having one windof said lines through the impedance simu-,

ing serially connected between said loops,

a telephone receiver and a condenser con nected 1n shunt with said loops at the midpoint of the serial winding, and a telephone transmitter connected serially to the other winding of said transformer.

5. A telephone system comprisingtwo lines which may normally be interconnected for telephonic communication, a telephone set comprising a telephone receiver shunting a pair of inductances at their. mid-point, said of said lines while no cominnnication maybe established between theparties at the ends of saidlines, comprising an iron core transformer, one winding of which is connected in series with said l 1nes,a telephone receiver, a condenser, said telephone receiver and said condenser being connected in shunt with said lines at the nid point ofthe winding in series therewith, and a telephone transmitter connected to the otherwinding of said transformer.

telephone system comprising a tele- 5 phone loop, a first inductance in series with said telephone loop, a telephone receiver, a

condenser, said-reeeiverand said condenser bridging said loop. between the mid-point of said first inductance and one terminal ofsaid said inducloop, a second inductance coupled to the first inductance, a telephone transmitter in series with said second inductance, a call circuit, a

network having an impedance substantially equal to the impedance of said call circuit, and means for connecting the network or: the call circuit between the terminal of the first inductance and the same terminal of thetelephone loop to which the receiver and condenser are connected. i

8. A telephone systemcomprising a telephone loop, a first inductance connected to one terminal of said telephone loop, a telephone receiver, a condenser, said receiver and said condenser bridging said loop between the midpoint of first inductance and theiother terminal of said loop, a second inductance coupled to the first inductance, a telephone transmitter in series with said second inductance, and a network of suitable impedance connected between the second terminal of the loop and the other terminal of the first inductance. V I

In testimony whereof, I have signed my name to this specification this 5th day of July, 1927. I

EGINHARD DIETZE. 

